PageRenderTime 23ms CodeModel.GetById 13ms app.highlight 6ms RepoModel.GetById 1ms app.codeStats 1ms

/arch/x86/kernel/crash_dump_32.c

https://gitlab.com/Team-OSE-old/SimpleKernel
C | 95 lines | 52 code | 13 blank | 30 comment | 8 complexity | ea80cddc31c5ea14f4bd58e565af047f MD5 | raw file
 1/*
 2 *	Memory preserving reboot related code.
 3 *
 4 *	Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 5 *	Copyright (C) IBM Corporation, 2004. All rights reserved
 6 */
 7
 8#include <linux/slab.h>
 9#include <linux/errno.h>
10#include <linux/highmem.h>
11#include <linux/crash_dump.h>
12
13#include <asm/uaccess.h>
14
15static void *kdump_buf_page;
16
17static inline bool is_crashed_pfn_valid(unsigned long pfn)
18{
19#ifndef CONFIG_X86_PAE
20	/*
21	 * non-PAE kdump kernel executed from a PAE one will crop high pte
22	 * bits and poke unwanted space counting again from address 0, we
23	 * don't want that. pte must fit into unsigned long. In fact the
24	 * test checks high 12 bits for being zero (pfn will be shifted left
25	 * by PAGE_SHIFT).
26	 */
27	return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
28#else
29	return true;
30#endif
31}
32
33/**
34 * copy_oldmem_page - copy one page from "oldmem"
35 * @pfn: page frame number to be copied
36 * @buf: target memory address for the copy; this can be in kernel address
37 *	space or user address space (see @userbuf)
38 * @csize: number of bytes to copy
39 * @offset: offset in bytes into the page (based on pfn) to begin the copy
40 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
41 *	otherwise @buf is in kernel address space, use memcpy().
42 *
43 * Copy a page from "oldmem". For this page, there is no pte mapped
44 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
45 *
46 * Calling copy_to_user() in atomic context is not desirable. Hence first
47 * copying the data to a pre-allocated kernel page and then copying to user
48 * space in non-atomic context.
49 */
50ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
51                               size_t csize, unsigned long offset, int userbuf)
52{
53	void  *vaddr;
54
55	if (!csize)
56		return 0;
57
58	if (!is_crashed_pfn_valid(pfn))
59		return -EFAULT;
60
61	vaddr = kmap_atomic_pfn(pfn);
62
63	if (!userbuf) {
64		memcpy(buf, (vaddr + offset), csize);
65		kunmap_atomic(vaddr);
66	} else {
67		if (!kdump_buf_page) {
68			printk(KERN_WARNING "Kdump: Kdump buffer page not"
69				" allocated\n");
70			kunmap_atomic(vaddr);
71			return -EFAULT;
72		}
73		copy_page(kdump_buf_page, vaddr);
74		kunmap_atomic(vaddr);
75		if (copy_to_user(buf, (kdump_buf_page + offset), csize))
76			return -EFAULT;
77	}
78
79	return csize;
80}
81
82static int __init kdump_buf_page_init(void)
83{
84	int ret = 0;
85
86	kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
87	if (!kdump_buf_page) {
88		printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
89			 " page\n");
90		ret = -ENOMEM;
91	}
92
93	return ret;
94}
95arch_initcall(kdump_buf_page_init);